Optimized hip-knee-ankle exoskeleton assistance reduces the metabolic cost of walking with worn loads

Abstract Background Load carriage is common in a wide range of professions, but prolonged load carriage is associated with increased fatigue and overuse injuries. Exoskeletons could improve the quality of life of these professionals by reducing metabolic cost to combat fatigue and reducing muscle ac...

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Autores principales:	Gwendolyn M. Bryan, Patrick W. Franks, Seungmoon Song, Ricardo Reyes, Meghan P. O’Donovan, Karen N. Gregorczyk, Steven H. Collins
Formato:	article
Lenguaje:	EN
Publicado:	BMC 2021
Materias:	Exoskeleton Augmentation Load-carriage Human-in-the-loop optimization Neurosciences. Biological psychiatry. Neuropsychiatry RC321-571
Acceso en línea:	https://doaj.org/article/ba055b21c0ee48f4b3aa079851484930
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spelling	oai:doaj.org-article:ba055b21c0ee48f4b3aa0798514849302021-11-14T12:39:20ZOptimized hip-knee-ankle exoskeleton assistance reduces the metabolic cost of walking with worn loads10.1186/s12984-021-00955-81743-0003https://doaj.org/article/ba055b21c0ee48f4b3aa0798514849302021-11-01T00:00:00Zhttps://doi.org/10.1186/s12984-021-00955-8https://doaj.org/toc/1743-0003Abstract Background Load carriage is common in a wide range of professions, but prolonged load carriage is associated with increased fatigue and overuse injuries. Exoskeletons could improve the quality of life of these professionals by reducing metabolic cost to combat fatigue and reducing muscle activity to prevent injuries. Current exoskeletons have reduced the metabolic cost of loaded walking by up to 22% relative to walking in the device with no assistance when assisting one or two joints. Greater metabolic reductions may be possible with optimized assistance of the entire leg. Methods We used human-in the-loop optimization to optimize hip-knee-ankle exoskeleton assistance with no additional load, a light load (15% of body weight), and a heavy load (30% of body weight) for three participants. All loads were applied through a weight vest with an attached waist belt. We measured metabolic cost, exoskeleton assistance, kinematics, and muscle activity. We performed Friedman’s tests to analyze trends across worn loads and paired t-tests to determine whether changes from the unassisted conditions to the assisted conditions were significant. Results Exoskeleton assistance reduced the metabolic cost of walking relative to walking in the device without assistance for all tested conditions. Exoskeleton assistance reduced the metabolic cost of walking by 48% with no load (p = 0.05), 41% with the light load (p = 0.01), and 43% with the heavy load (p = 0.04). The smaller metabolic reduction with the light load may be due to insufficient participant training or lack of optimizer convergence. The total applied positive power was similar for all tested conditions, and the positive knee power decreased slightly as load increased. Optimized torque timing parameters were consistent across participants and load conditions while optimized magnitude parameters varied. Conclusions Whole-leg exoskeleton assistance can reduce the metabolic cost of walking while carrying a range of loads. The consistent optimized timing parameters across participants and conditions suggest that metabolic cost reductions are sensitive to torque timing. The variable torque magnitude parameters could imply that torque magnitude should be customized to the individual, or that there is a range of useful torque magnitudes. Future work should test whether applying the load to the exoskeleton rather than the person’s torso results in larger benefits.Gwendolyn M. BryanPatrick W. FranksSeungmoon SongRicardo ReyesMeghan P. O’DonovanKaren N. GregorczykSteven H. CollinsBMCarticleExoskeletonAugmentationLoad-carriageHuman-in-the-loop optimizationNeurosciences. Biological psychiatry. NeuropsychiatryRC321-571ENJournal of NeuroEngineering and Rehabilitation, Vol 18, Iss 1, Pp 1-13 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Exoskeleton Augmentation Load-carriage Human-in-the-loop optimization Neurosciences. Biological psychiatry. Neuropsychiatry RC321-571
spellingShingle	Exoskeleton Augmentation Load-carriage Human-in-the-loop optimization Neurosciences. Biological psychiatry. Neuropsychiatry RC321-571 Gwendolyn M. Bryan Patrick W. Franks Seungmoon Song Ricardo Reyes Meghan P. O’Donovan Karen N. Gregorczyk Steven H. Collins Optimized hip-knee-ankle exoskeleton assistance reduces the metabolic cost of walking with worn loads
description	Abstract Background Load carriage is common in a wide range of professions, but prolonged load carriage is associated with increased fatigue and overuse injuries. Exoskeletons could improve the quality of life of these professionals by reducing metabolic cost to combat fatigue and reducing muscle activity to prevent injuries. Current exoskeletons have reduced the metabolic cost of loaded walking by up to 22% relative to walking in the device with no assistance when assisting one or two joints. Greater metabolic reductions may be possible with optimized assistance of the entire leg. Methods We used human-in the-loop optimization to optimize hip-knee-ankle exoskeleton assistance with no additional load, a light load (15% of body weight), and a heavy load (30% of body weight) for three participants. All loads were applied through a weight vest with an attached waist belt. We measured metabolic cost, exoskeleton assistance, kinematics, and muscle activity. We performed Friedman’s tests to analyze trends across worn loads and paired t-tests to determine whether changes from the unassisted conditions to the assisted conditions were significant. Results Exoskeleton assistance reduced the metabolic cost of walking relative to walking in the device without assistance for all tested conditions. Exoskeleton assistance reduced the metabolic cost of walking by 48% with no load (p = 0.05), 41% with the light load (p = 0.01), and 43% with the heavy load (p = 0.04). The smaller metabolic reduction with the light load may be due to insufficient participant training or lack of optimizer convergence. The total applied positive power was similar for all tested conditions, and the positive knee power decreased slightly as load increased. Optimized torque timing parameters were consistent across participants and load conditions while optimized magnitude parameters varied. Conclusions Whole-leg exoskeleton assistance can reduce the metabolic cost of walking while carrying a range of loads. The consistent optimized timing parameters across participants and conditions suggest that metabolic cost reductions are sensitive to torque timing. The variable torque magnitude parameters could imply that torque magnitude should be customized to the individual, or that there is a range of useful torque magnitudes. Future work should test whether applying the load to the exoskeleton rather than the person’s torso results in larger benefits.
format	article
author	Gwendolyn M. Bryan Patrick W. Franks Seungmoon Song Ricardo Reyes Meghan P. O’Donovan Karen N. Gregorczyk Steven H. Collins
author_facet	Gwendolyn M. Bryan Patrick W. Franks Seungmoon Song Ricardo Reyes Meghan P. O’Donovan Karen N. Gregorczyk Steven H. Collins
author_sort	Gwendolyn M. Bryan
title	Optimized hip-knee-ankle exoskeleton assistance reduces the metabolic cost of walking with worn loads
title_short	Optimized hip-knee-ankle exoskeleton assistance reduces the metabolic cost of walking with worn loads
title_full	Optimized hip-knee-ankle exoskeleton assistance reduces the metabolic cost of walking with worn loads
title_fullStr	Optimized hip-knee-ankle exoskeleton assistance reduces the metabolic cost of walking with worn loads
title_full_unstemmed	Optimized hip-knee-ankle exoskeleton assistance reduces the metabolic cost of walking with worn loads
title_sort	optimized hip-knee-ankle exoskeleton assistance reduces the metabolic cost of walking with worn loads
publisher	BMC
publishDate	2021
url	https://doaj.org/article/ba055b21c0ee48f4b3aa079851484930
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Optimized hip-knee-ankle exoskeleton assistance reduces the metabolic cost of walking with worn loads

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